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David E Morris

Publications and source records attributed to David E Morris.

At least 19 recordsLinked to original sources
PubMed2006

Ytterbocene charge-transfer molecular wire complexes.

A systematic study of the novel charge-transfer [(f)14-(pi)0-(f)14 --> (f)13-(pi)2-(f)13] electronic state found in 2:1 metal-to-ligand adducts of the type [(Cp)2Yb](BL)[Yb(Cp)2] [BL = tetra(2-pyridyl)pyrazine (tppz) (1), 6',6' '-bis(2-pyridyl)-2,2':4',4'':2'',2'''-quaterpyridine (qtp) (2), 1,4-di(terpyridyl)-benzene (dtb) (3), Cp = (C5Me5)] has been conducted with the aim of determining the effects of increased Yb-Yb separation on the magnetic and electronic properties of these materials. The neutral [(f)13-(pi)2-(f)13], cationic [(f)13-(pi)1-(f)13] and dicationic [(f)13-(pi)0-(f)13] states of these complexes were studied by cyclic voltammetry, UV-vis-NIR electronic absorption spectroscopy, NMR, X-ray crystallography, and magnetic susceptibility measurements. The spectroscopic and magnetic data for the neutral bimetallic complexes is consistent with an [(f)13(pi)2(f)13] ground-state electronic configuration in which each ytterbocene fragment donates one electron to give a singlet dianionic bridging ligand with two paramagnetic Yb(III) centers. The voltammetric data demonstrate that the electronic interaction in the neutral molecular wires 1-3, as manifested in the separation between successive metal reduction waves, is large compared to analogous transition metal systems. Electronic spectra for the neutral and monocationic bimetallic species are dominated by pi-pi and pi-pi transitions, masking the f-f bands that are expected to best reflect the electronic metal-metal interactions. However, these metal-localized transitions are observed when the electrons are removed from the bridging ligand via chemical oxidation to yield the dicationic species, and they suggest very little electronic interaction between metal centers in the absence of pi electrons on the bridging ligands. Analysis of the magnetic data reveals that the qtp complex displays antiferromagnetic coupling of the type Yb(alpha)(alphabeta)Yb(beta) at approximately 13 K.

Journal Article↗
PubMed2006

Post-chemotherapy gross tumor volume is predictive of survival in patients with stage III non-small cell lung cancer treated with combined modality therapy.

PURPOSE: To evaluate the influence of clinical covariates, particularly pre-chemotherapy gross tumor volume (GTV), post-chemotherapy GTV, on overall survival in the treatment of stage III non-small cell lung cancer (NSCLC). METHODS AND MATERIALS: We retrospectively analyzed 102 patients who were enrolled on three consecutive clinical trials, which employed the treatment paradigm of two cycles of induction chemotherapy followed by thoracic radiation therapy. The pre-chemotherapy GTV, post-chemotherapy GTV, change in GTV, histology, disease stage, performance status, age, race, treatment with concurrent chemoradiotherapy versus radiotherapy alone were evaluated to determine their impact on overall survival. The log10 of the GTV was used to normalize the data and thereby reduce the impact of exceptionally large values. RESULTS: Both the log10 of the post-chemotherapy GTV and Eastern Cooperative Oncology Group (ECOG) performance status covariates were highly prognostic for overall survival (p = 0.006 and p = 0.008, respectively). Disease stage (at diagnosis) was also significant (p = 0.048). The log10 pre-chemotherapy GTV covariate was borderline significant (p = 0.067). The strongest prognostic model was the two-covariate model, which contained the log10 post-chemotherapy GTV and ECOG performance status covariates, (model chi2 of 18.67, with p = 0.001 for each covariate). CONCLUSIONS: The log10 post-chemotherapy GTV has significant prognostic survival value when the strategy of induction chemotherapy is employed in the treatment on stage III NSCLC. ECOG performance status and stage were also significant prognostic factors for survival.

Adult↗
PubMed2006

4f-5f heterotrimetallic complexes exhibiting electrochemical and magnetic communication.

Novel 4f-5f complexes of U(IV) and Th(IV) with Yb have been prepared using a terpyridyl-functionalized ketimide linking group. These 4f-5f heterotrimetallic complexes (C5Me5)2An[-N=C(CH2C6H5)(tpyYb(C5Me5)2)]2 (where An = Th, U) exist in Yb(II/III) valence equilibria and exhibit rich electrochemical behavior consistent with electronic coupling between the actinide and Yb(II/III)tpy*- moieties. The magnetic response of the uranium complex, studied qualitatively using a subtraction method, is indicative of a coupled magnetic state between the U(IV) and Yb(III)tpy*- groups at low temperatures. Both the electrochemical and magnetic data are in agreement and are consistent with differences in participation of the actinide valence orbitals in the ketimide bonding.

Journal Article↗
PubMed2006

Clinical role of proton magnetic resonance spectroscopy in oncology: brain, breast, and prostate cancer.

Standardised proton magnetic resonance spectroscopic imaging (MRSI) was initially developed for routine in-situ clinical assessment of human brain tumours, and its use was later extended for examination of prostate and breast cancers. MRSI coupled with both routine and functional MRI techniques provides more detailed information about a tumour's location and extent of its infiltration than any other modality alone. Information obtained by adding MRSI data to anatomical and functional MRI findings aid in clinical management decisions (such as watchful waiting vs immediate intervention). In this Review, we discuss the current status of proton MRSI, with emphasis on its clinical use to map the location and extent of tumour processes for spectroscopic image-guided biopsy procedures and to monitor treatment paradigms for brain, prostate, and breast cancer.

Brain Neoplasms↗
PubMed2006

The emergence of a unique population in non-small cell lung cancer: systemic or loco-regional relapse following postoperative adjuvant platinum-based chemotherapy.

Surgical resection remains the foundation of curative therapy in early stage non-small cell lung cancer (NSCLC). Recent evidence from several randomized trials has shown that adjuvant chemotherapy regimens of platinum-based agents plus third-generation cytotoxic agents improve survival rates in this population of patients. Despite the use of adjuvant chemotherapy, many patients will suffer a relapse, typically systemic, and be candidates for subsequent therapies. This represents a new population of patients with NSCLC. To date, there are no published trials that evaluate prognostic factors or therapeutic outcomes in these patients. Although therapeutic paradigms have been established in patients who present with de novo metastatic NSCLC, it is not clear whether these paradigms are successful for patients who relapse following platinum-based adjuvant chemotherapy. The influence of time from the previous adjuvant exposure is likely to be as important as it seems to be in other solid tumors. However, dedicated clinical research has not yet established this paradigm in NSCLC and the influence this should have on the choice of subsequent therapy is unknown. The nature of the prior adjuvant exposure may also play a role in the choice of subsequent therapy. This has implications for the design of future trials in advanced NSCLC as these patients may or may not have the same natural history as the de novo metastatic NSCLC patient. Future clinical trials are required to address these issues as well as the biologic heterogeneity that likely exists between patients who are seemingly cured by surgery, relapse early (<1 year), or at later times following adjuvant therapy.

Carcinoma, Non-Small-Cell Lung↗
PubMed2006

Current and evolving treatment options for limited stage small cell lung cancer.

PURPOSE OF REVIEW: About one-third of small cell lung cancer cases are classified as limited stage. Trials have attempted to establish the most effective, least toxic regimen of combined modality treatment. Recently, issues like the role of the positron emission tomography scan, elderly patient management and the timing and delivery of radiotherapy have been addressed. Several targeted agents have also been evaluated. This review will highlight the data that have greatly impacted on the standard of limited stage small cell lung cancer care. RECENT FINDINGS: Trials have concluded that small cell lung cancer is fluorodeoxy-D-glucose avid and that positron emission tomography has potential for utility in staging and radiation therapy planning, though it is not recommended. Recent trials confirm no benefit to adding chemotherapeutic agents to standard cisplatin and etoposide. To date, all targeted therapies have failed to show impressive results. Two analyses of outcomes in elderly patients argue that combined modality therapy should be considered, with patients carefully monitored. Two meta-analyses demonstrate thoracic radiotherapy should be delivered, with increased dose and schedule intensity. SUMMARY: Current data demonstrate that combined modality therapy with early administration of thoracic radiotherapy remains the care standard in limited stage small cell lung cancer care. Cisplatin and etoposide continue to be the chosen cytotoxic agents. Targeted therapies and advances in the radiotherapy technological aspects represent opportunities for improved outcomes in the future management of this aggressive disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

The American Society for Therapeutic Radiology and Oncology (ASTRO) evidence-based review of the role of radiosurgery for brain metastases.

PURPOSE: To systematically review the evidence for the use of stereotactic radiosurgery in adult patients with brain metastases. METHODS: Key clinical questions to be addressed in this evidence-based review were identified. Outcomes considered were overall survival, quality of life or symptom control, brain tumor control or response and toxicity. MEDLINE (1990-2004 June Week 2), CANCERLIT (1990-2003), CINAHL (1990-2004 June Week 2), EMBASE (1990-2004 Week 25), and the Cochrane library (2004 issue 2) databases were searched using OVID. In addition, the Physician Data Query clinical trials database, the proceedings of the American Society of Clinical Oncology (ASCO) (1997-2004), ASTRO (1997-2004), and the European Society of Therapeutic Radiology and Oncology (ESTRO) (1997-2003) were searched. Data from the literature search were reviewed and tabulated. This process included an assessment of the level of evidence. RESULTS: For patients with newly diagnosed brain metastases, managed with whole-brain radiotherapy alone vs. whole-brain radiotherapy and radiosurgery boost, there were three randomized controlled trials, zero prospective studies, and seven retrospective series (which satisfied inclusion criteria). For patients with up to three (<4 cm) newly diagnosed brain metastases (and in one study up to four brain metastases), radiosurgery boost with whole-brain radiotherapy significantly improves local brain control rates as compared with whole-brain radiotherapy alone (Level I-III evidence). In one large randomized trial, survival benefit with whole-brain radiotherapy was observed in patients with single brain metastasis. In this trial, an overall increased ability to taper down on steroid dose and an improvement in Karnofsky performance status was seen in patients who were treated with radiosurgery boost as compared with patients treated with whole-brain radiotherapy alone. However, Level I evidence regarding overall quality of life outcomes using a validated instrument has not been reported. All randomized trials showed improved local control with the addition of radiosurgery to whole-brain radiotherapy. For patients with multiple brain metastases, there is no overall survival benefit with the use of radiosurgery boost to whole-brain radiotherapy (Level I-III evidence). Radiosurgery boost is associated with a small risk of early or late toxicity. In patients treated with radiosurgery alone (withholding whole-brain radiotherapy) as initial treatment, there were 2 randomized trials, 2 prospective cohort studies, and 16 retrospective series. There is Level I to Level III evidence that the use of radiosurgery alone does not alter survival as compared to the use of whole-brain radiotherapy. However, there is Level I to Level III evidence that omission of whole-brain radiotherapy results in poorer intracranial disease control, both local and distant (defined as remaining brain, outside the radiosurgery field). Quality of life outcomes have not been adequately reported. Radiosurgery is associated with a small risk of early or late toxicity. Radiosurgery as salvage for patients with brain metastases was reported in zero randomized trials, one prospective study, and seven retrospective series. CONCLUSIONS: Based on Level I-III evidence, for selected patients with small (up to 4 cm) brain metastases (up to three in number and four in one randomized trial), the addition of radiosurgery boost to whole-brain radiotherapy improves brain control as compared with whole-brain radiotherapy alone. In patients with a single brain metastasis, radiosurgery boost with whole-brain radiotherapy improves survival. There is a small risk of toxicity associated with radiosurgery boost as compared with whole-brain radiotherapy alone. In selected patients treated with radiosurgery alone for newly diagnosed brain metastases, overall survival is not altered. However, local and distant brain control is significantly poorer with omission of upfront whole-brain radiotherapy (Level I-III evidence). Whether neurocognition or quality of life outcomes are different between initial radiosurgery alone vs. whole-brain radiotherapy (with or without radiosurgery boost) is unknown, because this has not been adequately tested. There was no statistically significant difference in overall toxicity between those treated with radiosurgery alone vs. whole-brain radiotherapy and radiosurgery boost based on an interim report from one randomized study. There is insufficient evidence as to the clinical benefit/risks radiosurgery used in the setting of recurrent or progressive brain metastases, although radiographic responses are well-documented.

Brain Neoplasms↗
PubMed2005

The American Society for Therapeutic Radiology and Oncology (ASTRO) evidence-based review of the role of radiosurgery for malignant glioma.

PURPOSE: To systematically review the evidence for the use of stereotactic radiosurgery or stereotactic fractionated radiation therapy in adult patients with malignant glioma. METHODS: Key clinical questions to be addressed in this evidence-based review were identified. Outcomes considered were overall survival, quality of life or symptom control, brain tumor control or response and toxicity. MEDLINE (1990-2004 June Week 2), CANCERLIT (1990-2003), CINAHL (1990-2004 June Week 2), EMBASE (1990-2004 Week 25), and the Cochrane library (2004 issue 2) databases were searched using OVID. In addition, the Physician Data Query clinical trials database, the proceedings of the American Society of Clinical Oncology (1997-2004), ASTRO (1997-2004), and the European Society of Therapeutic Radiology and Oncology (ESTRO) (1997-2003) were searched. Data from the literature search were reviewed and tabulated. This process included an assessment of the level of evidence. RESULTS: For patients with newly diagnosed malignant glioma, radiosurgery as boost therapy with conventional external beam radiation was examined in one randomized trial, five prospective cohort studies, and seven retrospective series. There is Level I evidence that the use of radiosurgery boost followed by external beam radiotherapy and carmustine (BCNU) does not confer benefit with respect to overall survival, quality of life, or patterns of failure as compared with external beam radiotherapy and BCNU. There is Level I-III evidence of toxicity associated with radiosurgery boost as compared with external beam radiotherapy alone. The results of the prospective and retrospective studies may be influenced by selection bias. Radiosurgery used as salvage for recurrent or progressive malignant glioma after conventional external beam radiotherapy failure was reported in zero randomized trials, three prospective cohort studies, and five retrospective series. The available data are sparse and insufficient to make absolute recommendations. Stereotactic fractionated radiation therapy has been reported as boost therapy with external beam radiotherapy for patients with newly diagnosed malignant glioma in only three prospective studies. As primary therapy alone without conventional external beam radiotherapy for newly diagnosed malignant glioma patients, stereotactic fractionated radiation therapy has been reported in only one prospective study. There were only three prospective series and two retrospective studies reported for patients with recurrent or progressive malignant glioma. CONCLUSIONS: For patients with malignant glioma, there is Level I-III evidence that the use of radiosurgery boost followed by external beam radiotherapy and BCNU does not confer benefit in terms of overall survival, local brain control, or quality of life as compared with external beam radiotherapy and BCNU. The use of radiosurgery boost is associated with increased toxicity. For patients with malignant glioma, there is insufficient evidence regarding the benefits/harms of using radiosurgery at the time progression or recurrence. There is also insufficient evidence regarding the benefits/harms in the use of stereotactic fractionated radiation therapy for patients with newly diagnosed or progressive/recurrent malignant glioma.

Adult↗
PubMed2005

Ligand substituent effect observed for ytterbocene 4'-cyano-2,2':6',2' '-terpyridine.

A new N-heterocyclic complex of ytterbocene (Cp(2)Yb(II), Cp = C(5)Me(5)) has been prepared by the addition of 4'-cyano-2,2':6',2' '-terpyridine (tpyCN) to Cp(2)Yb(II)(OEt(2)) in toluene to give a dark blue species designated as Cp(2)Yb(tpyCN). The effect of the electron-withdrawing group (-CN) on the redox potentials of the charge-transfer form of this complex [in which an electron is transferred from the f(14) metal center to the lowest unoccupied (pi) molecular orbital of the tpyCN ligand to give a 4f(13)-pi(1) electronic configuration] has been quantified by cyclic voltammetry. The tpyCN ligand stabilizes this configuration by 60 mV more than that in the unsubstituted tpy ligand complex and by 110 mV more than that in the unsubstituted bpy ligand complex. Magnetic susceptibility measurements corroborate the enhanced stabilization of the 4f(13)-pi(1) configuration by the substituted terpyridyl ligand complex. Furthermore, the temperature dependence of the magnetic data is most consistent with a thermally induced valence tautomeric equilibrium between this paramagnetic 4f(13)-pi(1) form that dominates near room temperature and the diamagnetic 4f(14)-pi(0) form that dominates at low temperature. Differing coordination modes for the tpyCN ligand to the ytterbocene center have also been confirmed by isolation and X-ray crystallographic characterization of complexes binding through either the cyano nitrogen of tpyCN or the three terpyridyl nitrogen atoms of tpyCN.

Journal Article↗
PubMed2005

Evidence-based review of three-dimensional conformal radiotherapy for localized prostate cancer: an ASTRO outcomes initiative.

PURPOSE: To perform a systematic review of the evidence to determine the efficacy and effectiveness of three-dimensional conformal radiotherapy (3D-CRT) for localized prostate cancer; provide a clear presentation of the key clinical outcome questions related to the use of 3D-CRT in the treatment of localized prostate cancer that may be answered by a formal literature review; and provide concise information on whether 3D-CRT improves the clinical outcomes in the treatment of localized prostate cancer compared with conventional RT. METHODS AND MATERIALS: We performed a systematic review of the literature through a structured process developed by the American Society for Therapeutic Radiology and Oncology's Outcomes Committee that involved the creation of a multidisciplinary task force, development of clinical outcome questions, a formal literature review and data abstraction, data review, and outside peer review. RESULTS: Seven key clinical questions were identified. The results and task force conclusions of the literature review for each question are reported. CONCLUSION: The technological goals of reducing morbidity with 3D-CRT have been achieved. Randomized trials and follow-up of completed trials remain necessary to address these clinical outcomes specifically with regard to patient subsets and the use of hormonal therapy.

Disease-Free Survival↗
PubMed2005

Molecular spectroscopy of uranium(IV) bis(ketimido) complexes. rare observation of resonance-enhanced raman scattering from organoactinide complexes and evidence for broken-symmetry excited states.

Electronic absorption and resonance-enhanced Raman spectra for ketimido (azavinylidene) complexes of tetravalent uranium, (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) (R = Ph, Me, and CH(2)Ph), have been recorded. The absorption spectra exhibit four broad bands between 13 000 and 24 000 cm(-1). The highest-energy band is assigned to the ketimido-localized p( perpendicular)(N)-->pi(N=C) transition based on comparison to the spectra of (C(5)H(5))(2)Zr[-N=CPh(2)](2) and (C(5)Me(5))(2)Th[-N=CPh(2)](2). Upon excitation into any of these four absorption bands, the (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) complexes exhibit resonance enhancement for several Raman bands attributable to vibrations of the ketimido ligands. Raman bands for both the symmetric and nominally asymmetric N=C stretching bands are resonantly enhanced upon excitation into the p( perpendicular)(N)-->pi(N=C) absorption bands, indicating that the excited state is localized on a single ketimido ligand. Raman excitation profiles for (C(5)Me(5))(2)U[-N=CPh(2)](2) confirm that at least one of the lower-energy electronic absorption bands (E(max) approximately 16300 cm(-1)) is a charge-transfer transition between the U(IV) center and the ketimido ligand(s). The observations of both charge-transfer transitions and resonance enhancement of Raman vibrational bands are exceedingly rare for tetravalent actinide complexes and reflect the strong bonding interactions between the uranium 5f/6d orbitals and those on the ketimido ligands.

Journal Article↗
PubMed2004

Systematic review evaluating the timing of thoracic radiation therapy in combined modality therapy for limited-stage small-cell lung cancer.

PURPOSE: We employed meta-analytic techniques to evaluate early (E) versus late (L) timing of thoracic radiation therapy (RT) in limited-stage small-cell lung cancer (LS-SCLC). In addition, we assessed the impact of radiation fractionation and chemotherapeutic regimen on timing. METHODS: Randomized trials published after 1985 addressing timing of RT relative to chemotherapy in LS-SCLC were included. Trials were analyzed by risk ratio (RR), risk difference, and number-needed-to-treat methods. RESULTS: Overall survival (OS) RRs for all studies were 1.17 at 2 years (95% CI, 1.02 to 1.35; P = .03) and 1.13 at 3 years (95% CI, 0.92 to 1.39; P = .2), indicating a significantly increased 2-year survival for ERT versus LRT patients and suggestive of a similar trend at 3 years. Subset analysis of studies using hyperfractionated RT revealed OS RR for ERT versus LRT of 1.44 (95% CI, 1.17 to 1.77; P = .001) and 1.39 (95% CI, 1.02 to 1.90; P = .04) at 2 and 3 years, respectively, indicating a survival benefit of ERT versus LRT. Studies using once-daily fractionation showed no difference in 2- and 3-year OS RRs for ERT compared with LRT. Studies using platinum-based chemotherapy had OS RRs of 1.30 (95% CI, 1.10 to 1.53; P = .002) and 1.35 (95% CI, 1.07 to 1.70; P = .01) at 2 and 3 years, respectively, favoring ERT. Studies using nonplatinum-based chemotherapy regimens had nonsignificant differences in OS. CONCLUSION: A small but significant improvement in 2-year OS for ERT versus LRT in LS-SCLC was observed, similar to the benefit of adding RT to chemotherapy or prophylactic cranial irradiation. A greater difference was evident for hyperfractionated RT and platinum-based chemotherapy.

Carcinoma, Non-Small-Cell Lung↗
PubMed2004

Induction and concurrent chemotherapy with high-dose thoracic conformal radiation therapy in unresectable stage IIIA and IIIB non-small-cell lung cancer: a dose-escalation phase I trial.

PURPOSE: Local control rates at conventional radiotherapy doses (60 to 66 Gy) are poor in stage III non-small-cell lung cancer (NSCLC). Dose escalation using three-dimensional thoracic conformal radiation therapy (TCRT) is one strategy to improve local control and perhaps survival. PATIENTS AND METHODS: Stage III NSCLC patients with a good performance status (PS) were treated with induction chemotherapy (carboplatin area under the curve [AUC] 5, irinotecan 100 mg/m(2), and paclitaxel 175 mg/m(2) days 1 and 22) followed by concurrent chemotherapy (carboplatin AUC 2 and paclitaxel 45 mg/m(2) weekly for 7 to 8 weeks) beginning on day 43. Pre- and postchemotherapy computed tomography scans defined the initial clinical target volume (CTV(I)) and boost clinical target volume (CTV(B)), respectively. The CTV(I) received 40 to 50 Gy; the CTV(B) received escalating doses of TCRT from 78 Gy to 82, 86, and 90 Gy. The primary objective was to escalate the TCRT dose from 78 to 90 Gy or to the maximum-tolerated dose. RESULTS: Twenty-nine patients were enrolled (25 assessable patients; median age, 59 years; 62% male; 45% stage IIIA; 38% PS 0; and 38% > or = 5% weight loss). Induction CIP was well tolerated (with filgrastim support) and active (partial response rate, 46.2%; stable disease, 53.8%; and early progression, 0%). The TCRT dose was escalated from 78 to 90 Gy without dose-limiting toxicity. The primary acute toxicity was esophagitis (16%, all grade 3). Late toxicity consisted of grade 2 esophageal stricture (n = 3), bronchial stenosis (n = 2), and fatal hemoptysis (n = 2). The overall response rate was 60%, with a median survival time and 1-year survival probability of 24 months and 0.73 (95% CI, 0.55 to 0.89), respectively. CONCLUSION Escalation of the TCRT dose from 78 to 90 Gy in the context of induction and concurrent chemotherapy was accomplished safely in stage III NSCLC patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Seeking a home for a PET, part 3: Emerging applications of positron emission tomography imaging in the management of patients with lung cancer.

Positron emission tomography (PET) imaging is an important tool to refine the diagnosis and staging approach in patients with a possible lung cancer. In addition, other applications of PET imaging are being explored. Data consistently show that the intensity of uptake on a PET scan correlates with the biological aggressiveness of a tumor. PET imaging for restaging after induction therapy does not appear to be accurate enough to guide management. The results of PET imaging late after completion of treatment are highly predictive of future survival, and changes in PET images after only one cycle of chemotherapy are predictive of how a patient will respond to that planned treatment. PET imaging may allow radiotherapy treatment fields to be planned with greater accuracy, although data on how this affects patient outcomes are not yet available. Further technologic improvements in PET scanners are likely to bring further benefits to the management of patients with lung cancer in the future.

Combined Modality Therapy↗
PubMed2004

CT and MR imaging after placement of the GliaSite radiation therapy system to treat brain tumor: initial experience.

BACKGROUND AND PURPOSE: The GliaSite system delivers local, high radiation after brain tumor resection. We describe the imaging appearance of the device and the changes it causes. METHODS: Eight patients with brain tumors were treated with this system. After surgery, all underwent MR imaging, and one underwent CT. Five were examined 1 month after radioactive unloading and every 2 months thereafter (total, 6-9 months). Initial studies were assessed for balloon appearance and complications; subsequent studies, for signal intensity and enhancement. Three patients underwent multivoxel proton MR spectroscopy, and one underwent MR perfusion study. Spectra were reviewed for metabolites suggesting tumor; perfusion studies were reviewed for increased relative cerebral blood volume and flow. RESULTS: CT showed the hyperattenuating balloon with considerable artifact. All MR images showed the device and adjacent brain. Follow-up studies showed enhancement and T2 hyperintensity in five patients. In one, enhancement progressively disappeared with no evidence of tumor recurrence. Another patient had progressive enhancement and low relative cerebral blood volume and flow; biopsy showed necrosis and inflammation. One patient had progressive enhancement and high choline levels (proved anaplastic astrocytoma). In another, T2 signal intensity and contrast enhancement progressed owing to tumor and bacterial infection. The last patient had a high choline level (proved radionecrosis); enhancement progressed over 5 months. In three, the device was removed early because of bleeding, mass effect, and therapeutic changes (no follow-up). CONCLUSION: Good balloon visualization was possible with MR imaging. After brachytherapy, all patients developed T2 hyperintensity; stable or progressive enhancement occurred with tumor recurrence and radionecrosis. High choline levels were suggestive of, but not necessarily diagnostic of, tumor.

Aged↗
PubMed2003

Electrochemical and spectroscopic characterization of the novel charge-transfer ground state in diimine complexes of ytterbocene.

The novel charge-transfer ground state found in alpha,alpha'-diimine adducts of ytterbocene (C(5)Me(5))(2)Yb(L) [L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen)] in which an electron is spontaneously transferred from the f(14) metal center into the lowest unoccupied (pi*) molecular orbital (LUMO) of the diimine ligand to give an f(13)-L(*)(-) ground-state electronic configuration has been characterized by cyclic voltammetry, UV-vis-near-IR electronic absorption, and resonance Raman spectroscopies. The voltammetric data demonstrate that the diimine ligand LUMO is stabilized and the metal f orbital is destabilized by approximately 1.0 V each upon complexation for both bpy and phen adducts. The separation between the ligand-based oxidation wave (L(0/-)) and the metal-based reduction wave (Yb(3+/2+)) in the ytterbocene adducts is 0.79 V for both bpy and phen complexes. The UV-vis-near-IR absorption spectroscopic data for both the neutral adducts and the one-electron-oxidized complexes are consistent with those reported recently, but previously unreported bands in the near-IR have been recorded and assigned to ligand (pi*)-to-metal (f orbital) charge-transfer (LMCT) transitions. These optical electronic excited states are the converse of the ground-state charge-transfer process (e.g., f(13)-L(*-) <--> f(14)-L(0)). These new bands occur at approximately 5000 cm(-1) in both adducts, consistent with predictions from electrochemical data, and the spacings of the resolved vibronic bands in these transitions are consistent with the removal of an electron from the ligand pi* orbital. The unusually large intensity observed in the f --> f intraconfiguration transitions for the neutral phenanthroline adduct is discussed in terms of an intensity-borrowing mechanism involving the low-energy LMCT states. Raman vibrational data clearly reveal resonance enhancement for excitation into the low-lying pi* --> pi* ligand-localized excited states, and comparison of the vibrational energies with those reported for alkali-metal-reduced diimine ligands confirms that the ligands in the adducts are reduced radical anions. Differences in the resonance enhancement pattern for the modes in the bipyridine adduct with excitation into different pi* --> pi* levels illustrate the different nodal structures that exist in the various low-lying pi* orbitals.

Journal Article↗